Trailing edge optimized near field transducer

ABSTRACT

An energy assisted magnetic recording (EAMR) head for writing to a recording media is disclosed. The EAMR head includes a write pole for providing a magnetic field for writing to the recording media; and a near field transducer disposed adjacent to the write pole and comprising a disk section and a pin section extending towards an air bearing surface (ABS) from the disk section. At least a portion of the pin section is electrically isolated from the write pole by an insulator material.

FIELD OF THE INVENTION

The present invention generally relates to magnetic read/write headsand, in particular, relates to trailing edge optimized near fieldtransducers.

BACKGROUND

To increase the areal storage density of a magnetic recording device,the recording layer thereof may be provided with smaller and smallerindividual magnetic grains. This reduction in grain size soon reaches a“superparamagnetic limit,” at which point the magnetic grains becomethermally unstable and incapable of maintaining their magnetization. Thethermal stability of the magnetic grains can be increased by increasingthe magnetic anisotropy thereof (e.g., by utilizing materials withhigher anisotropic constants). Increasing the magnetic anisotropy of themagnetic grains, however, increases their coercivity and thereforerequires a stronger magnetic field to change the magnetic orientation ofthe grains (e.g., in a write operation).

Energy-assisted magnetic recording (EAMR) is used to address thischallenge. In an EAMR system, a small spot where data is to be writtenis locally heated to reduce the coercivity of the magnetic grainstherein for the duration of the write operation, thereby allowingmaterials with increased magnetic anisotropy to be used, and greaterareal storage density to be exploited. In EAMR approach, a semiconductorlaser diode is normally used as a light source and coupled to a planarwaveguide which serves as light delivery path. A grating structure maybe used to couple the laser light into the waveguide. Design challengesfor these grating structures include improving their coupling efficiencyand the difficulty in aligning a light source for high volumemanufacturing processes. The coupled light is then routed to a nearfield transducer (NFT) by which the optical energy is provided to asmall optical spot on the recording media a few tens of nanometers (nm)in size. The optical energy provided to the small optical spot generatesa thermal spot in the recording media.

In order to write at higher densities, a smaller thermal spot isdesired. Because the conventional magnetic recording medium typicallyincludes lower thermal conductivity underlayers, the thermal spot istypically larger than the optical spot. Thus an even smaller opticalspot is desired at higher densities. In order to obtain a smalleroptical spot, optical components within the conventional EAMR systemneed to be scaled down to small sizes. Fabrication of portions of theconventional NFT, at such small sizes may be challenging. For example, awidth of a pin section of the NFT (the “pin width”) becomes vanishinglysmall at high areal density. In addition, with a conventional NFTarrangement, the trailing edge of the thermal spot has a high degree ofcurvature, which limits the track density due to SNR degradation fromthe track curvature.

Accordingly, what is needed is a system and method for optimizing thetrailing edge of the thermal spot in a recording media.

BRIEF SUMMARY OF THE INVENTION

An energy assisted magnetic recording (EAMR) head for writing to arecording media is provided. The EAMR head can comprise a write pole forproviding a magnetic field for writing to the recording media. The EAMRhead can further comprise at least one laser for providing energy to therecording media to assist the writing. The EAMR head can furthercomprise a near field transducer (NFT) disposed adjacent to the writepole and coupled with the at least one laser, the NFT configured todirect the energy to a corresponding thermal spot on the recordingmedia. The NFT can comprise a disk section and a pin section extendingtowards an air bearing surface (ABS) from the disk section, wherein atleast a portion of the pin section is separated from the write pole byan insulating layer.

An energy assisted magnetic recording (EAMR) head for writing to arecording media is provided. The EAMR head can comprise a write pole forproviding a magnetic field for writing to the recording media. The EAMRhead can further comprise a near field transducer disposed adjacent tothe write pole and comprising a disk section and a pin section extendingtowards an air bearing surface (ABS) from the disk section, wherein atleast a portion of the pin section is electrically isolated from thewrite pole by an insulator material.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram depicting a cross-sectional view of an exemplaryEAMR head according to certain aspects of the subject disclosure.

FIG. 2 is a diagram depicting a perspective view of a conventional NFTarrangement that may be employed in an EAMR head.

FIG. 3 is a diagram depicting a cross-sectional view of an exemplary NFTarrangement according to certain aspects of the subject disclosure.

FIG. 4 shows a first simulated thermal spot associated with theexemplary NFT arrangement of FIG. 3 juxtaposed against a secondsimulated thermal spot associated with the conventional NFT arrangementof FIG. 2 according to certain aspects of the subject disclosure.

FIGS. 5A, 5B, and 5C are diagrams depicting exemplary first, second, andthird Puccini-type NFTs having non-rectangular pin cross sections,respectively, in a plane parallel to the ABS according to certainaspects of the subject disclosure.

FIG. 6 shows a first simulated thermal spot associated with a first NFTarrangement in which at least a pin section of a triangular NFT isseparated from the write pole by an insulator layer juxtaposed against asecond simulated thermal spot associated with a second NFT arrangementin which both disk and pin sections of the triangular NFT are separatedfrom the write pole by a conductive heat sink layer according to certainaspects of the subject disclosure.

FIG. 7 shows a first simulated thermal spot associated with a first NFTarrangement in which at least a pin section of a trapezoidal NFT isseparated from the write pole by an insulator layer juxtaposed against asecond simulated thermal spot associated with a second NFT arrangementin which both disk and pin sections of the trapezoidal NFT are separatedfrom the write pole by a conductive heat sink layer according to certainaspects of the subject disclosure.

FIG. 8 shows thermal spots at different skew angles that demonstrateskew angle track performance and the lower curvature obtained by the useof a trapezoidal NFT in accordance with one aspect of the subjectdisclosure.

DETAILED DESCRIPTION

FIG. 1 is a diagram depicting a cross-sectional view of an exemplaryEAMR head 100 according to certain aspects of the subject disclosure.The EAMR head 100 comprises a slider 101. The slider 101 comprises asubstrate 110, a recorder/reader layer 120 disposed over the substrate110, and an overcoat layer 130 disposed over the recorder/reader layer120. In certain embodiments, the substrate 110 comprises AlTiC and theovercoat layer 130 comprises alumina. The slider 101 has a leading edge107 and a trailing edge 109, and an air-bearing surface (ABS) 105 facinga magnetic recording medium 103. The recorder/reader layer 120 of theslider 101 includes a write pole 122 for recording or erasinginformation on the medium 103 by focusing a magnetic field on a spot onthe medium 103, a coil 124 for generating the magnetic field, a reader126 for reading a magnetic bit recorded on the medium 103, and awaveguide structure 150. The waveguide structure 150 includes a first,top clad layer 156 and a second, bottom clad layer 152 surrounding awaveguide core layer 154. In certain embodiments, the waveguidestructure 150 may further include a structure (e.g., a grating) that isconfigured to couple incident EM radiation 171 (e.g., optical beam froma laser) into the waveguide core layer 154 to form a coupled opticalbeam 172. The EAMR head 100 further includes an NFT arrangement 102 thatcomprises a near field transducer (NFT) 158 formed at a distal end ofthe waveguide structure 150 proximate the ABS 109. A conventional NFTarrangement/design 102″ is provided in FIG. 2, and a novel NFTarrangement 102″ according to certain aspects of the subject disclosureis provided in FIG. 3. The NFT 158 is configured to concentrate energyfrom the coupled optical beam 172 to a nano-sized optical spot 192 onthe recording medium 103 well below the diffraction limit from whichstandard focusing lenses suffer.

During the operation of a hard disk drive comprising the EAMR head 100,the magnetic recording medium 103 rotates at high speed, and air flowingat high speed between the ABS 105 and the magnetic recording medium 103provides an upward force to the slider 101 such that the slider 101 ismaintained at a certain height from the magnetic recording medium 103. Aportion of the incident EM radiation 171 arrived at the waveguidestructure 150 is coupled into the waveguide core layer 154 to form acoupled optical beam 172 traveling down the waveguide core layer 154toward the ABS 105. The energy from the coupled optical beam 172 isconcentrated onto a nano-sized optical spot 192 on the magneticrecording medium 103 by means of the NFT 158. At least a portion of thecoupled optical beam 172 (and its associated energy) exits the ABS 105in the form of a focused optical beam 173 and is concentrated onto anano-sized optical spot 192 on the recording medium 103. Some of theoptical energy delivered to the optical spot 192 is absorbed by andconverted into heat in the magnetic recording medium 103. Theopto-thermal conversion produces a thermal spot 194 on the recordingmedium 103. The thermal spot 194 on the magnetic recording medium 103 issubsequently subjected to a pulse of write magnetic field from the writepole 122.

FIG. 2 is a diagram depicting a perspective view of a conventional NFTarrangement 102′ that may be employed in an EAMR head (e.g., EAMR head100 of FIG. 1). The conventional NFT arrangement 102′ includes an NFT158′ separated from write pole 122 by a heat sink layer 230. In thedepicted example, the NFT 158′ is a “Puccini-type” NFT having a disksection 210 and a pin section 220 extending towards the ABS 105. The pinsection 220 has a rectangular cross-section in a plane parallel to theABS 105 along the entire length of the pin section 220. The NFT 158′ maycomprise of a metal (e.g., Au, Ag) capable of supporting asurface-plasmon resonance (SPR) therein. In the conventional NFTarrangement 102′, the disk and pin sections 210, 220 of the NFT 158′ arecoupled to and separated from the write pole 122 by the heat sink layer230 comprising a conductive metal (e.g., Cu) for efficiently dissipatingheat generated in the NFT 158 from the coupled optical beam 172 into thewrite pole 122.

In operation, an optical energy received from the coupled optical beam172 excites a surface-plasmon resonance (SPR) in the NFT 158′. As the EMenergy associated with the SPR travels down the pin section 220 towardsthe ABS 105, a portion of the EM energy flows into the write pole 122 inthe form of a skin-depth penetration through the conductive heat sinklayer 230. The portion of the EM energy thus penetrated into the writepole 122 travels down towards the ABS 105 in a separate path in thewrite pole 122 and creates a curvature in the trailing edge of thethermal spot 194.

FIG. 3 is a diagram depicting a cross-sectional view of an exemplary NFTarrangement 102″ according to certain aspects of the subject disclosure.For ease of illustration only, without any intent to limit the scope ofthe subject disclosure in any way, the following description of theexemplary NFT arrangement 102″ makes references to elements of the EAMRhead 100 of FIG. 1. However, one skilled in the art shall appreciatethat the various embodiments of the subject disclosure may be applied toother types of EAMR heads without departing from the scope of thesubject disclosure.

The exemplary NFT arrangement 102″ includes an NFT 158″ disposedadjacent to the write pole 122. In the illustrated embodiment, a disksection 310 of the NFT 158″ is separated from the write pole 122 by aheat sink layer 330, while a pin section 320 of the NFT 158″ isseparated from the write pole 122 by an insulator layer 340.

In certain embodiments, the NFT 158″ is a Puccini-type NFT having acircular disk section. In other embodiments, the disk section 310 of thePuccini-type NFT can have non-circular shapes including, but not limitedto, an oval, an elipse, a rectangle, a square, and other regular ornon-regular polygons. The pin section 320 can have a rectangularcross-section in a plane parallel to the ABS. Alternatively, the pinsection 320 can have a non-rectangular cross section in a plane parallelto the ABS as will be discussed in detail below with respect to FIGS.5A, 5B, and 5C.

In certain embodiments, the insulator layer 340 comprises anelectrically insulating material such as Si₃N₄, Al₂O₃, AlN, GaN, SiO₂,and BN₄. In some embodiments, the insulator layer 340 comprises athermally, but not electrically, insulating material. In the illustratedexample, the insulator layer 340 starts at a proximal end 322 of the pinsection 320 and extends beyond a distal end 324 of the pin section 320.In alternative embodiments, the insulator layer 340 may start from apoint in the disk portion 310 of the NFT 310 or a point in the pinsection 320 between the proximal and distal ends 322, 324 and may extendbeyond the distal end 324 or end at the distal end 324.

As with the conventional NFT arrangement of FIG. 2, an optical energyreceived from the coupled optical beam 172 excites a SPR in the NFT158″. As the EM energy associated with the SPR travels down the pinsection 320 towards the ABS 105, however, no significant portion of theEM energy flows into the write pole 122 because a skin-depth penetrationof the EM energy is prevented by the presence of the insulator layer 340disposed between the pin region 320 and the write pole 122. The absenceof the skin-depth penetration into the write pole 122, in turn, preventsor reduces a corresponding curvature in the trailing edge of the thermalspot 194 in the recording medium 103.

The heat sink layer 330 disposed between the disk section 310 and thewrite pole 122 provides an effective transfer of heat from the NFT 158″to the write pole 122. The heat sink layer 330 can comprise a metal thatcan provide such an effective heat transfer, non-limiting examples ofwhich include Cu, Agu, Ag, and Al. In some embodiments, the heat sinklayer 330 comprises a metal (e.g., Cu) that provides an effective heattransfer between the NFT 158″ and the write pole 122, yet does notitself support SPR or at least does not support SPR as effectively asthe material (e.g., Au) comprising the NFT 158″. This ensures that theSPR resonance excited in the NFT 158″ is either not sufficientlyextended into the heat sink layer 330 and possibly into the write pole122, thereby preventing another source of energy draw from the NFT 158″.

At least the disk section 310 of the NFT 158″ comprises a metal capableof supporting SPR in the disk section when subjected to the opticalenergy 172. The metal can be, for example, Au, Ag, Cu, Al, or acombination thereof. In some embodiments, the disk section 310 and thepin section 320 of the NFT 158″ comprise one if such metals. In oneparticular embodiment, the disk and pin sections 31, 320 are made of Au.The disk region 310 (and the pin section 320) can have a thickness 312in an along-track direction of between about 10 and 100 nm. The diskregion 310 (and the pin section 320) can have a width in a cross-trackdirection of between about 10 and 500 nm. The insulator layer 340 (andthe heat sink layer 330) can have a thickness 342 in an along-trackdirection of between about 10 and 100 nm. The insulating layer 340 (andthe heat sink layer 330) can have a width in a cross-track direction ofbetween about 10 and 200 nm.

FIG. 4 shows a first simulated thermal spot 410 associated with theexemplary NFT arrangement 102″ of FIG. 3 juxtaposed against a secondsimulated thermal spot 420 associated with the conventional NFTarrangement 102′ of FIG. 2. In both cases, the NFTs 158′, 158″ areassumed to be a Puccini pin having a rectangular disk section 210, 310and a rectangular pin cross section. The NFTs 158′, 158″ are assumed tobe comprised of Au and the heat sink layers 230, 330 are assumed to beCu. The trailing edge of the thermal spot 410 terminates at the NFT anddoes not extend substantially into a region of recording medium 103below write pole (e.g., 122). By contrast, the trailing edge of thethermal spot 420 extends beyond the NFT and into a region 403 of therecording medium 103 below write pole (e.g., 122).

In the illustrated embodiment of FIG. 3, the pin section 320 of the NFT158″ has a rectangular cross-section in a plane parallel to the ABS. Inother embodiments of the subject disclosure, the NFT 158″ may have anon-rectangular pin cross section, at least at its distal end facing theABS 105. Such a non-rectangular pin cross section can further optimize(e.g. flatten) the trailing edge of the thermal spot produced by theNFT. By utilizing a pin with a non-rectangular (e.g., trapezoidal)cross-section, a number of advantages are provided including optimizing(e.g. flattening) the trailing edge of the thermal spot, increasing thethermal gradient at the transition, which provides for a more efficientEAMR writing, and lessening the transition curvature, which provides fora better shingle EAMR implementation and better track performance withskew angle. FIG. 8 show thermal spots at different skew angles thatdemonstrate skew angle track performance and the lower curvatureobtained by the use of a trapezoidal NFT in accordance with one aspectof the subject disclosure.

FIGS. 5A, 5B, and 5C are diagrams depicting exemplary first, second, andthird Puccini-type NFTs 158A, 158B, 158C having non-rectangular pincross sections 502A, 502B, 502C, respectively, in a plane parallel tothe ABS, at least at distal ends of pin sections 520A, 520B, 520C. Inthe first NFT 158A, the non-rectangular pin cross section 502A istriangular. In the second NFT 158B, the non-rectangular pin crosssection is trapezoidal. The pin section 520C of the third NFT 158C has arectangular pin cross section at its proximal end facing the disksection 510 and the triangular pin cross section 502C at its distal endfacing the ABS.

A multitude of variations can be made to the NFTs 158A, 158B, 158Cwithout departing from the scope of the subject disclosure. For example,the NFTs may have other non-rectangular cross-sectional shapesincluding, but not limited to, a semicircle. a semi-polygon (e.g., anupper half of a hexagon or octagon), and a chevron. The disk 510 mayhave non-circular shapes including, but not limited to, an oval, anelipse, a rectangle, a square, and other regular or non-regularpolygons. The pin section 520C of the third NFT 158C may have anon-rectangular cross sectional shape other than a triangle (e.g.,trapezoid, chevron) at its distal end.

FIG. 6 shows a first simulated thermal spot 610 juxtaposed against asecond simulated thermal spot 620. In both cases, the NFTs are assumedto be a Puccini-type NFT (e.g., 158A of FIG. 5A) having a triangular pincross section (e.g., 502A). An outline 501 of the triangular pin crosssection is indicated in FIG. 6. The first thermal spot 610 (left) isassociated with a first NFT arrangement in which a disk section of theNFT is separated from the write pole by a conductive heat sink layer(e.g., Cu) while a pin section of the NFT is separated from the writepole by an insulator layer (e.g., Si₃N₄). By contrast, the secondthermal spot 620 (right) is associated with a second NFT arrangement inwhich both of the disk and pin sections of the NFT are separated fromthe write pole by a conductive heat sink layer (e.g., Cu). The trailingedge of the thermal spot 610 terminates substantially at the NFT (e.g.,the triangular pin cross section 601) and does not extend substantiallyinto a region of recording medium 103 below write pole (e.g., 122),resulting in a very flat trailing edge. By contrast, the trailing edgeof the thermal spot 620 extends beyond the NFT and into a region 603 ofrecording medium 103 below write pole (e.g., 122). The comparison of thethermal spots 610, 620 illustrates that in a head with a NFT coupled toa write pole, an NFT arrangement having the combination of anon-rectangular NFT pin cross section and an insulator layer between theNFT's pin section and the write pole minimizes the trailing edgecurvature.

FIG. 7 shows a first simulated thermal spot 710 juxtaposed against asecond simulated thermal spot 720. In both cases, the NFTs are assumedto be a Puccini-type NFT (e.g., 158C of FIG. 5A) having a trapezoidalpin cross section (e.g., 502B). The first thermal spot 710 (left) isassociated with a first NFT arrangement in which a disk section of theNFT is separated from the write pole by a conductive heat sink layer(e.g., Cu) while a pin section of the NFT is separated from the writepole by an insulator layer (e.g., Si₃N₄). By contrast, the secondthermal spot 729 (right) is associated with a second NFT arrangement inwhich both disk and pin sections of the NFT is separated from the writepole by a conductive heat sink layer (e.g., Cu). The trailing edge ofthe thermal spot 710 terminates substantially at the NFT and does notextend into a region of recording medium 103 below write pole (e.g.,122). By contrast, the trailing edge of the thermal spot 720 extendsbeyond the NFT and into a region 703 of recording medium 103 below writepole (e.g., 122), A trapezoidal NFT (e.g., 158B) can have certainadvantages including an easier manufacturability and a larger area forheat sinking into the write pole over a triangular NFT (e.g., 158A). Thebetter heat sinking capability improves thermal reliability of an EAMRhead incorporating a trapezoidal NFT.

Those skilled in the art shall appreciate that various NFT arrangementsof subject disclosure provide a number of advantages includingoptimizing (e.g., flattening) the trailing edge of the thermal spot inan EAMR disk drive, e.g., by preventing or reducing skin-depthpenetration of energy into the write pole and/or by providing anon-rectangular NFT cross section. The optimized trailing edge, in turn,can help EAMR heads incorporating the various NFT arrangements achieve ahigher track density.

The description of the invention is provided to enable any personskilled in the art to practice the various embodiments described herein.While the present invention has been particularly described withreference to the various figures and embodiments, it should beunderstood that these are for illustration purposes only and should notbe taken as limiting the scope of the invention.

There may be many other ways to implement the invention. Variousfunctions and elements described herein may be partitioned differentlyfrom those shown without departing from the spirit and scope of theinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and generic principles definedherein may be applied to other embodiments. Thus, many changes andmodifications may be made to the invention, by one having ordinary skillin the art, without departing from the spirit and scope of theinvention.

A reference to an element in the singular is not intended to mean “oneand only one” unless specifically stated, but rather “one or more.” Theterm “some” refers to one or more. Underlined and/or italicized headingsand subheadings are used for convenience only, do not limit theinvention, and are not referred to in connection with the interpretationof the description of the invention. All structural and functionalequivalents to the elements of the various embodiments of the inventiondescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and intended to be encompassed by the invention.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe above description.

1. An energy assisted magnetic recording (EAMR) head for writing to arecording media, the EAMR head comprising: a write pole for providing amagnetic field for writing to the recording media; at least one laserfor providing energy to the recording media to assist the writing; anear field transducer (NFT) disposed adjacent to the write pole andcoupled with the at least one laser, the NFT configured to direct theenergy to a corresponding thermal spot on the recording media, whereinthe NFT comprises a disk section and a pin section extending towards anair bearing surface (ABS) from the disk section, and wherein the disksection is separated from the write pole by a heat sink layer and atleast a portion of the pin section is separated from the write pole byan insulating layer.
 2. The EAMR head of claim 1, wherein at least thedisk section of the NFT comprises a first material capable of supportinga surface-plasmon resonance in the disk section when subjected to theenergy.
 3. The EAMR head of claim 2, wherein the first material isselected from a group consisting of Au, Ag, Cu, and Al.
 4. The EAMR headof claim 1, wherein the disk section of the NFT comprises asubstantially circular disk comprising Au.
 5. The EAMR head of claim 1,wherein the disk section and the pin section of the NFT comprise Au. 6.The EAMR head of claim 2, wherein the disk section is coupled to thewrite pole via a heat sink layer comprising a second material.
 7. TheEAMR head of claim 6, wherein the disk region of the NFT has a thicknessin a range between about 10 and 100 nm, and the heat sink layer has athickness in a range between about 10 and 100 nm.
 8. The EAMR head ofclaim 6, wherein the second material is selected from a group consistingof Cu, Au, Ag, and Al.
 9. The EAMR head of claim 6, wherein the firstmaterial exhibits a stronger surface-plasmon resonance than the secondmaterial.
 10. The EAMR head of claim 6, wherein the first material isAu, and the second material is Cu.
 11. The EAMR head of claim 1, whereinthe corresponding thermal spot does not extend into a region of therecording media below the write pole.
 12. The EAMR head of claim 1,wherein the insulating layer prevents a skin depth penetration of theenergy into a corresponding portion of the write pole adjacent to theinsulating layer.
 13. The EAMR head of claim 1, wherein the pin sectionhas a rectangular cross section in a plane parallel to the ABS.
 14. TheEAMR head of claim 1, wherein the pin section has a non-rectangularcross section in a plane parallel to the ABS.
 15. The EAMR head of claim1, wherein the pin section has a thickness in an along-track directionof between about 10 and 100 nm.
 16. The EAMR head of claim 1, whereinthe pin section has a width in a cross-track direction of between about10 and 500 nm.
 17. The EAMR head of claim 1, wherein the insulatinglayer has a thickness of between about 10 and 100 nm.
 18. The EAMR headof claim 1, wherein the insulator layer comprises a material selectedfrom a group consisting of Si₃N₄, Al₂O₃, AlN, GaN, SiO₂, and BN₄. 19.The EAMR head of claim 1, wherein the EAMR head is configured to write aplurality of radially-spaced overlapping data tracks of data on therecording media.
 20. The EAMR head of claim 1, wherein the correspondingspot has a width not less than a track pitch of the recording media. 21.An energy assisted magnetic recording (EAMR) head for writing to arecording media comprising: a write pole for providing a magnetic fieldfor writing to the recording media; and a near field transducer disposedadjacent to the write pole and comprising a disk section and a pinsection extending towards an air bearing surface (ABS) from the disksection, wherein the disk section is separated from the write pole by aheat sink layer and at least a portion of the pin section iselectrically isolated from the write pole by an insulator material.